html,
body {
  width: 100vw;
  height: 100vh;
  padding: 0;
  margin: 0;
  overflow: hidden;
  background: #1a1a1a;
  display: flex;
  justify-content: center;
  align-items: center;
}

#pong {
  background: #222;
  box-shadow: 0 0 30px #000;
  display: block;
  border-radius: 8px;
}